Ultra high frequency energy coupling



Dec. 23, 1947. J. F. ZALESKI ULTRA-HIGH-FREQUENCY ENERGY COUPLING FiledApril a, 1943 INVENTOR JOHN F. ZALESKI m-ro muzv Patented Dec. 23, 1947ULTRA HIGH FREQUENCY ENERGY COUPLING John F. Zaleski, Queens Village, N.Y., assignor to Sperry Gyroscope Company, Inc., a corporation of NewYork Application April 8, 1943, Serial No. 482,341

14 Claims. 1 The present invention is related to the art including ultrahigh frequency energy-conducting apparatus, and, more specifically,relates to such conducting apparatus of the wave guide or dielectricguide type.

When transferring energy between a source and a load at ultra highfrequencies or microwaves having wavelengths of the order of centimetersor less, it has become customary to utilize so-called wave guides ordielectric guides, which essentially comprise a hollow energy-conductingmember having a boundary whose dielectric constant is different fromthat of the surrounding medium. Most usually, such boundaries are formedby thin metallic shells or pipes of various cross-sections, but may alsobe formed by pipes of dielectric material which may be hollow or solid,as is well known. Such apparatus will be termed wave guides in thefollowing specification.

When coupling a source to a load by means of a high frequency waveguide, it is well known that certain precautions are necessary to assurefull utilization of the capacity of the conducting system at highestefficiency. For this purpose it is necessary to match the source to theload to avoid the production of standing waves in the wave guide, whichproduce local high current intensities and increase losses in additionto decreasing the power flow through the conducting apparatus.

Considered from one viewpoint, a standing wave may be considered to becaused by the reflection of a wave traveling in the wave guide by adiscontinuity in the conducting medium, such as may be caused by asudden change of impedance of the medium, as where a change in dimensionoccurs or an impedance different from the characteristic impedance ofthe wave guide is connected to the wave guide. The reflected Wave thusproduced inter-acts with the forwardtraveling wave to produce a standingwave. Such a standing wave may be eliminated by having an additionalreflected wave introduced in the wave guide such that its phase isopposite and its magnitude equal to that of the reflected wave producedby the change in guide dimension or impedance. The phase and magnitudemeasurements of the two reflected waves must, of course, be made at thesame oint along the wave guide. sual y, all undesired reflection occurswhere a load is connected to the wave guide. Therefore, to eliminate theresulting standing waves, a second reflection must be provided havingthe proper characteristics to cancel the effect of the first undesiredreflection. Apparatus for producing such a canceling reflection isusually termed an impedance transformer or an impedancematching device.As already discussed, such an impedance transformer must correlate boththe amplitude and phase of the reflection it produces with that of theundesired reflection. Therefore,

two independent adjustments for such an impedance transformer arenecessary to permit adjustment of its reflection to cancel that producedby the undesired impedance discontinuity. Roughly speaking, theseadjustments may correspond respectively to amplitude adjustment andphase adjustment of the reflected wave produced thereby. Usually,however, one adjustment of the impedance transformer will produce acombination of amplitude and phase change in the reflected wave, and theother adjustment will likewise produce a combination of amplitude andphase change. So long as these combinations of amplitude and phasechange are independent of one another, the two adjustments of theimpedance transformer will be sufficient to match substantially any loadto any source.

In the prior art it has been known to provide two separate adjustmentsfor a wave guide impedance transformer in the form of adjustable stubwave guides connected in shunt with the main energy-conducting waveguide at separated points thereof. Such impedance-matching devices,while, useful, are inconvenient because of the extra, space required forlocating them separately along the wave guide, and also because atcertain spacings, correlated to multiples of a quarter-wavelength of theoperating frequency, these separate adjustable devices are no longerindependent of one another, so that the utility of the device issomewhat restricted.

According to the present invention, an improved form ofimpedance-matching device is provided, in which two adjustments may bemade at the same location along the wave guide, and which permitsmatching the impedances connected at either end of the wave guidesection carrying the matching device over a wide range of values. In thepresent instance, this is done by providing a stub section in shunt withthe main wave guide section and having an adjustable slidingshort-circuiting piston plunger whose adjustment provides one of the twonecessary matching adjustments. In addition to this, the resent deviceutilizes a conductor extending axially of the stub section and into themain wave guide, the amount of projection of this axial or innerconductor into the main wave guide being adjustable to provide thesecond required impedance-matching adjustment. In this manner bothadjustments may be made at the same point, decreasing the spacerequirements of the impedance-matching device, and having a simplerconstruction by avoiding the necessity for dual sliding pistons as inprior devices, whereby the apparatus of the invention may be more simplymanufactured and easily utilized.

The present invention is also adapted for use together with rotatable orotherwise adjustable wave guide joints, for producing a proper impedancematch in the system when energy is conducted through such joints, asfrom a stationary source to a movable load, or vice versa.

Accordingly, it is an object of the present invention to provide animproved impedancematching device or impedance transformer for ultrahigh frequency energy.

It is another object of the present invention to provide an improvedultra high frequency impedance-matching device or transformer having apair of adjustments at substantially the same location.

It is a further object of the present invention to provide an improvedultra high frequency impedance-matching device or transformer having apair of conveniently adjustable portions for eliminating standing waves.

It is yet another object of the present invention to provide an improvedform of impedance transformer or matching device which may be utilizedto eliminate standing waves in ultra high frequency wave guides whichmay be fixed or relatively adjustable or rotatable.

It is another object of the present invention to provide an improvedultra high frequency impedance-matching or transforming device which issimple in construction and easy of adjustment.

It is a further object of the present invention to provide improvedrotatable or adjustable joints for ultra high frequency wave guideswhich present a minimum of hindrance and a maximum of efficiency to theflow of ultra high frequency energy therethrough.

It is another object of the present invention to provide improvedadjustable or rotatable joints for ultra high frequency wave guidesutilizing an impedance transformer or matching device of theabove-mentioned type for avoiding the production of standing waves,whereby increased efliciency and extended utility are derived.

Other objects and advantages of the present invention will becomeapparent from the specification, taken in connection with theaccompanying drawing wherein the invention is embodied in concrete form.

In the drawing,

Fig. 1 shows a longitudinal cross-sectional view of the impedancetransformer of the present invention operating in conjunction with afixed wave guide section.

Fig. 2 shows a longitudinal cross-sectional view of an improvedrotatable wave guide joint in cooperation with the impedance transformerof the present invention.

' Fig. 3 shows a cross-section of Fig. 2 along line 33 thereof.

Fig. 4 shows a cross-section of a modification of a portion of Fig.2.

Fig, 5 shows a longitudinal cross-sectional View of a modification ofthe invention of Fig. 2, also utilizing the impedance transformer 0f t Pent invention.

Referring to the drawing, and especially to Fig. 1, reference numeral IIdesignates a main section of Wave guide adapted to conduct ultra highfrequency energy from a source connected at one end to a load connectedat the other end. Wave guide I! is illustrated as being rectangular incross-section, although it is to be understood that any other shape ofcross-section may be utilized, as desired or required by characteristicsof the system. In order to match the impedance of the load to that ofthe source, Fig. 1 shows the impedance transformer E2 of the presentinvention, which comprises a tubular conductor l3 whose interiorcommunicates with the interior of the wave guide Ii. Tube [3 is providedwith a closure member or plug M at its upper end suitably conductivelyfixed within tube 23, as by pressing, soldering, welding or any othersuitable manner. Plug M is centrally drilled and tapped to receive acorrespondingly threaded rod which may be provided with a screw slot Hat its upper end, whereby, upon rotation of rod it, it may be axiallyinserted for an adjustable distance Within wave guide H, as shown. Thelower end of rod I6 is preferably slightly rounded to provide a smootherimpedance adjustment and to eliminate sharp edges which may createcorona effects at high electric field intensities and low barometricpressures such as may be encountered if the device is utilized onaircraft. However, any desired termination for the rod !6 may beutilized Where the above considerations do not apply.

Surrounding rod l6 and within tube i3 is a sliding piston l8 which makessliding contact with the inner wall of tube l3 and with the outersurface of rod It. Piston 18 may be suitably adjusted by a controlmember l9 connected thereto and passing through openings 2i in plug it.In this way it will be seen that rod it may be adjusted independently ofpiston l 8. By making suitable adjustments of these two adjustablemembers, the impedances of the load and source connected to oppositeends of Wave guide ii may be matched to eliminate standing waves in theWave guide H. This could, of course, be indicated by any suitable typeof standing wave indicator known to the art. In this manner theimpedance transformer l2 of the present invention provides a simplyconstructable and easily adjustable impedance transformer operable overa wide range of impedance adjustments and frequencies of operation.

Fig. 2 illustrates the use of the impedance transformer of Fig. 1 with arotatable wave guide joint. In the present instance, ultra highfrequency energy is conducted between two wave guides 22 and 23 whichare movable in parallel planes and are rotatable about an axis mutuallyperpendicular to these planes and passing through the wave guides 22 and23. As is discussed more in detail in copending application Serial No.447,524, granted September 10. 1946, as Patent 2,407,318, for Highfrequency apparatus, filed June 18, 1942, in the names of W. W. Mieherand J. D. Mallett, it is desirable to utilize the so-called TM mode ofenergization of a wave guide in which a rotatable joint is interposed inorder to prevent modulation of the ultra high frequency energy due tothe rotation of the two portions of the device, and also to producemaximum efficiency of energy transfer across the gap between the tworelatively rotatable portions of the device.

Accordingly, in the present system of Fig, 2, the

wave guides 22 and 23, which are illustrated again as being rectangular,although they need not be necessarily so, are coupled by a I'M-excitedsection of circular wave guide 24 comprising adjacent cylindricalsections 24' and 24" in which the joint is placed, and the impedancetransformer of the invention is utilized, in addition to itsimpedance-matching functions, to transform energ from the rectangularwave guide 22, which is usually excited in the TE mode, to theTM-excited circular wave guide 24. Thus, in Fig. 2 the rod 16 of theimpedance transformer I2 is extended completely across the wave guide 22and axially into the circular wave guide 24 through a gap 26 in theopposite wall 21 of wave guide 22. This wall 21 is made of appreciablethickness so that it forms a short section of concentric transmissionline with rod [5. By a proper choice of the thickness of wall 21 andupon proper setting of rod I6 and piston 18, the entire coupling may bemade relatively insensitive to changes in frequency. The rod l6 projectsbeyond the wall 21 axially of the circular wave guide 24 and therebyacts as an antenna to launch the TM mode of high frequency energy alongthe circular wave guide 24.

The wave guide 24 is formed in two sections 24 and 24" which areseparated by a gap 28 whereby they may be relatively adjusted.Surrounding the gap 28 and communicating therewith is the wave trap 29which acts to prevent high frequency energy from leaking or radiatingfrom gap 28. Wave trap 29 is formed by a pair of sleeves 3B, 30" mountedconcentrically with respect to the two part 24 and 24" of guide 24, andonly slightly spaced therefrom. Sleeves 3t, 39" are connected to andsupported from the respective sections 24', 24" by annular pieces 58',56", which are spaced from the gap 28 by substantially a quarter wavelength of the operating frequency.

In this manner, sleeves 3e, 39" form respective short circuited quarterwave transmission line sections and present a very high impedancelooking outward from gap 28, so that little energy is lost through gap28. Any impedance mismatch caused by gap 28 may be compensated for by asuitable setting of impedance transformer I2. It will be understood thatany suitable type of wave trap may be utilized here, including any ofthe types shown in the above-mentioned Patent No. 2,407,313.

The portions of Fig. 2 thus far described serve to efficiently transferultra high frequency energy between wave guide 22 and Wave guide 24. Itis also necessary to provide a similar apparatus for permittingefficient transmission of energy between wave guide 23 and wave guide24. If desired, the apparatus thus far described may be repeated, thatis, a second impedance transformer 12 identical to that alreadydescribed may be utilized in the same manner to couple wave guide 23 andWave guide 24. However, this would necessitate making four separateadjustments when adjusting the system to optimum operation.

According to the present invention, it has been found possible toprovide a non-adjustable coupling between wave guide 23 and wave guide24, while still permitting the two adjustments of transformer [2 toconveniently and efiiciently match the entire system over a suitablerange of frequencies. For this purpose, the wave guide 24 is caused tocommunicate directly with the wave uide 23 which is disposed at rightangles thereto. By making the length of the wave guide 24 exactly equalto one-half wavelength or an integral multiple thereof of the operatingfrequency, as measured within wave guide 24 with the TM mode ofenerglzation, it has been found that a resonant condition is producedwhich very conveniently and efliciently serves to couple wave guide 23to the circular wave guide 24 while still permittin proper matching bymeans of transformer l2.

If desired, the coupling between wave guide 23 and wave guide 24 may bemodified slightly to provide an even more eflicient coupling of theTE-mode energy in the rectangular wave guide 23 with the TM mode energyin the circular wave guide 24, as shown in Fig. 4 which illustrates amodification of a portion of the apparatus of Fig. 2. In this instance,the bottom of the circular Wave guide 24" is supplied with a recessedcylindrical portion 3| whose diameter and depth are so selected thatthis recessed portion 3| acts substantially as a short-circuited,quarter-wave guide for the TM mode of energy in wave guide 24, whilealso acting as a short-circuited, half-wave wave guide for the TE modein the circular wave guide 24. In this way any tendency for the TE modeto be set up in the wave guide 24 is substantially eliminated, andsubstantially only pure TM mode energy is permitted to exist in.the waveguide 24.

Fig. 5 shows another embodiment of the present invention in which arotatable wave guide joint similar to that of Fig. 2 is provided.However, in this instance, the two wave guides 22 and 23 are coupled bya section of concentric transmission line 32 rather than by the circularwave guide 24, as in the prior figure. Effectively, the device of Fig. 5may be considered to be formed by extending the thickness of wall 21 ofFig. 2 to join with the wall of wave guide 23. The rod 1 6 of theimpedance transformer l2 of Fig. 2 is then extended to form the centralconductor of this line 32 and extends further into the wave guide 22 insomewhat the manner shown in Fig, 1. The gap 33 is also formed in theouter conductor of line 32 and cooperates with the wave trap 34 in thesame manner as in Fig. 2.

If desired, the position of the rod relative to the short-circuited endsof wave guides 22 and 23 may be adjusted in the device of Fig, 5 byproviding the adjustable shorting plugs '36 and 31 therein respectively.A similar adjustment may be provided in the case of Fig. 2. Preferablythese shorting plugs are set for a particular frequency or for aparticular range of operating frequencies, and after being once set, areno longer adjusted. The onl adjustments then necessary to provideoptimum operation are those of rod i6 and piston E8 of the transformer52, in the manner already described with respect to Figs. 1 and 2. Inthis manner a simple, efiicient, and easily adjustable, rotatable waveguide joint is provided.

It is to be noted that the rotatable joint of Figs. 2 and 5 has thegreat advantage that all adjustments are made at a single point.Therefore, it is not necessary to have access to both ends of thecoupling guide 24 or line so the construction of the apparatus andremaining apparatus associated therewith is substantially simplifiedbecause the necessary bearings and supports for the relatively rotatableapparatus, while not shown in the present case, since they form no partof the present invention, may materially complicate the spacerequirements for the various portions of the system. By rendering theadjustments accessible at asingl point and taking up space at but asingle location, the

construction-pf the entire-apparatus; isrendered muchmore simplesAs-imany changes could-be-made in; the above construction and many"apparently widely different-embodiments of this-invention could bemade-without departing from the scope thereof, it is, intended that allmatter contained in the above description or shown'in" the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

Whatis claimed is:

1.- Ultra hi hfrequency apparatus for transforming animpedanceconnectedto a wave guide section, comprising-a. tubularconductor connected to-and-communicating with said-wave guide sectionintermediate the ends thereof,'a solid conductive rod supportedcoaxiallywithin said, tubular member and projecting transversel within said waveguide and havingv an end therein means for adjusting the position of theend of said rod withinsaidwave guide, and means for adjustabl"short-circuiting said tubular member and said rod, whereby animpedanceconnected. at one end of said wave guide section maybe transformed to adiiferent value at the other endthereof by adjusting the amount of saidrod-projection and said short-circuited means.

2. In. combination with. a hollow-pipe wave guide having a first openingfor entrance of ultra high frequency electromagnetic waves, a secondopening for discharging electromagnetic waves, and-a third openingintermediate said first and second openings, the apparatus comprising atubular conductor adjoining said wave guide at said third opening andextending therefrom externally of saidwave guide, a solid innerconductor supported substantially coaxially within said tubularconductor and projecting through said third opening into said wave guideand terminatingtherein, an axially movable conductive element connectingsaid tubular conductor to said inner con-ductorfor varying the impedanceat said opening between said tubular conductor and said inner conductor,and means-for adjusting the length of said inner conductor projectingwithin said wave guide for varying the coupling thereof with said waveguide.

3. In combination with a hollow-pipe wave guide coupled to a source ofultra-high frequency energy and also coupled to a load for said energyto transmit energy from said source to said load, said wave guide havingan opening through the wall thereof intermediate said source and saidload; the apparatus comprising a tubular conductor adjoining said waveguide at said opening and extending therefrom externally of said waveguide, a solid inner conductor supported coaxially within said tubularconductor and projecting through said opening into said Wave guide andhaving an end therein, and an axially movable conductive elementconnecting said tubular conductor to said inner conductor for varyingthe impedance at said opening between said tubular conductor and saidinner conductor.

4. Ultra high frequency apparatus for transforming an impedanceconnected to a section of hallow ultra high frequenc energy conductor,comprising an adjustable length of concentric transmission lineconnected to said conductor intermediate the ends thereof and having asolid inner conductor positioned within said hollow conductor, and meansfor adjusting the position of said inner conductor Within said hollowconductor, whereby an impedance connected at one end of said hollowconductor section may be transformed'to a different-impedance value atthe opposite end of said conductor by adjusting the length of saidconcentric line section and the position of said inner conductor.

5. An ultra high frequency variable impedance network for attachment toa ho11owpipe wave guide, comprising a tubular conductor adapted to bejoined to said wave guide at an opening therethrough to extend from saidopening angularly to and exteriorly of said Wave guide, a solid rodpositioned coaxially within and extending beyond said tubular conductorfor projecting through said opening into said wave guide for couplingtherewith, means for-varying the axial position of said rod, and meansfor adjustably short-circuiting said tubular conductor and-said rod,whereby the impedance presented to said wave guide may be varied.

6. Ultra high frequency variable impedance wave guide apparatus,comprising a section of hollow-pipe wave guide having an opening throughthe conductive wall intermediate the ends thereof, tubularccnductorjoined to said wave guide wall at said opening and extendingtherefrom exteriorly and transversely to said wave guide, an axiallyadjustable solid rod positioned coaxially within said tubular conductorand extending therefrom through said opening into said wave guide, meansfor adjusting the position of said rod within said wave guide, andmeansfor adjustably short-circuiting said tubular conduc tor and said rod,whereby theimpedance of said Wave guide may be adjusted as desired.

7. Apparatus for transferring ultra high frequency energy between ahollow-pipe wave guide conductor and another ultra high frequency energyconductor, comprising a section of circular wave guide, means includingan adjuscable section of concentric transmission line, on said Waveguide conductor and cooperating with aligned openings in said waveguideconductor and said wave guide section for coupling said wave guidesection to said wave guide conductor in a manner to excite TM waves insaid wave guide section,

means for coupling said circular wave guide section. to the other ofsaid conductors to transfer said TM energy to said other conductor, saidcircular wave guide section having a length substantially equal to anintegral multiple of half wavelengths of said TM energy mode in saidcircular wave guide section.

8. Apparatus for transferring ultra high frequency energy between twoultra high frequency energy conductors comprising a, section of circularwave guide, means for coupling said wave guide to one of said conductorsin a manner to excite TM waves in said wave guide section, means forcoupling said circular wave guide section to the other of saidconductors to transfer said TM energy to said other conductor, saidcircular wave guide section having a length sub stantially equal to anintegral multiple of half wavelengths of said TM energy mode in saidcircular wave guide section, one of said conductors comprising arectangular wave guide and one of said coupling means comprising anadjustable section of concentric transmission line havin the innerconductor thereof extending across said rectangular wave guide andcoaxially within said circular wave guide section, and means foradjusting the amount of projection of said inner conductor within saidcircular wave guide.

9. Apparatus for-transferring ultra high frequency energy comprising twospaced wave guides adapted to propagate energy in substantially'paralleldirections, a first conductor extending perpendicularly with respect tosaid wave guides, completely across one of said wave guides and into theother of said wave guides, a hollow tubular conductor concentricallysurrounding said first conductor between said wave guides and forming aconcentric transmission line section therewith, a second hollowconductor concentrically surrounding the portion of said first conductorprojecting on the other side of said first wave guide and forming aconcentric transmission line section therewith, means for adjustablyshort-circuiting said first conductor and said second hollow conductor,and means for adjusting the projection of said first conductor withinsaid other wave guide, whereby ultra high frequency energy may betransferred between said wave guides substantially without reflection orthe creation of standing waves by suitably adjusting saidshort-circuiting means and the amount of projection.

10. Apparatus for transferring ultra-high-frequency energy comprisingtwo spaced ultra-highfrequency energy conductors adapted to transmitenergy in substantially parallel directions, one of said conductorsbeing a rectangular wave guide, a section of circular wave guide formedof two relatively rotatable coaxial portions fixed respectively to saidconductors and having an axis of propagation substantially perpendicularto said conductors, whereby said two conductors may be rotated relativeto one another without interfering with the flow of ultra-high-frequencyenergy therebetween, means for coupling said wave guide to one of saidconductors in a manner to excite TM waves in said circular wave guidesection, and means for coupling said circular wave guide section to theother of said conductors to transfer said TM energy to said otherconductor, one of said coupling means comprising an adjustable sectionof concentric transmission line having the inner conductor thereofextending across said rectangular wave guide and coaxially within saidcircular wave guide section.

11. The apparatus defined in claim 10, further including means foradjusting the amount of projection of said inner conductor within saidcircular wave guide,

12. Apparatus for transferring ultra-high-frequency energy between twowave guides, comprising a first conductor extending completely acrossone of said wave guides and into the other of said wave guides, a firsthollow tubular conductor concentrically surrounding said first conductorbetween said wave guides and formin a concentric transmission linesection therewith, a second hollow conductor concentrically surroundingthe portion of said first conductor projecting on the other side of saidfirst wave guide and forming a concentric transmission line sectiontherewith, means for adjustably short-circuiting said first conductorand said second hollow conductor, and means for adjusting the projectionof said first conductor within said other wave guide, wherebyultra-high-frequency energy may be transferred between said wave guidessubstan tially without reflection or the creation of standing waves bysuitably adjusting said short-circuiting means and the amount ofprojection, said hollow tubular conductor being formed in two relativelyrotatable sections, and said first conductor being supported solely fromsaid second hollow conductor whereby said wave guides may be rotatedrelative to one another substantially without influencing the flow ofhigh frequency energy therebetween.

13. Apparatus for transferring ultra-high-frequency energy between twowave guides, comprising a section of concentric transmission lineextending between openings through the sides of said wave guides andhaving the inner conductor thereof projecting within one of said waveguides transversely thereof, means for adjusting the amount said innerconductor projects within said one wave guide to vary the couplingthereto, a short-circuited stub concentric transmission line connectingsaid inner conductor and the other of said wave guides, and means foradjusting the effective electrical length of said stub line.

14. Apparatus for transferring ultra-high-frequency energy comprising apair of wave guides having openings in the side walls thereof, a sectionof coaxial transmission line extending between said openings, said linehaving its outer conductor formed of two relatively rotatable coaxialsections connected respectively to said two guides and also having aunitary inner conductor fixed relative to one of said outer conductorsections and to its connected guide and projected transversely withinthe other of said guides short of the wall thereof, opposite said line.

JOHN F. ZALESKI.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS FOREIGN PATENTS Country Date Australia Nov. 4,1942 Number Number

